Mitral valve regurgitation (MR) is a functional heart disease under which the valve does not close completely and causes blood to leak back into the left atrium. This condition increases the workload on the heart and, if left untreated, can lead to irreversible heart damage, cardiac arrhythmia and congestive heart failure. Currently, mitral valve repair, as the intervention is called, requires open heart surgery with cardiopulmonary bypass. Under such conditions, the patient is subjected to intra- and post-operative trauma that can result in mortality increase and that can prevent high-risk individuals from undergoing the intervention. Hence the need to develop alternative procedures such as minimally invasive percutaneous interventions, which would greatly reduce the trauma and risks associated with conventional surgery, resulting in an increase of the number of potential candidates for repair, while significantly cutting patient's recovery times from weeks to days.
More specifically, a heart condition is often the result of a weakened heart caused by many factors such as age and lifestyle, among others. This weakening is manifested in an enlargement of the organ, which can affect the valve closing. Moreover, when a valve is affected by a disease, its malfunctioning deteriorates the myocardium's normal performance.
When the mitral valve leaks, blood flows backwards into the lungs. Under these conditions, the ventricle must pump more blood with each contraction to produce the same forward output of blood throughout the body. The heart, through remodeling, can compensate for this volume overload for many months or years. However, an enlargement of the left ventricle will eventually lead to annulus dilation and/or restricted leaflet motion, which will aggravate MR; an unstable system develops, where the heart is trapped in vicious cycle leading, ultimately, to its failure. For effective treatment, it is necessary to stop the cycle and, if possible, reverse the induced anatomical changes. The severity of MR is required to guide the patient's subsequent management and is assessed using different quantitative parameters.
Chronic MR is usually classified in three categories mild (1+), moderate (2+, 3+) and severe (4+). Generally the bigger the regurgitant volume, the more severe the patient condition. Mitral valve repair is usually required for symptomatic patients with a 3+ and 4+ angiographic grade. To function properly, the mitral valve requires the coordinated function of its different elements, as well as both left cardiac chambers: if one of these structures malfunctions, MR eventually occurs. In particular, since the annulus function is to support the leaflets, any variation in its geometry, will directly affect the closure of the leaflets and the valve area.
Over the years, annuloplasty has been the foundation of surgical mitral valve repair. There are two general methods of open-heart annuloplasty: (i) suture-based (rarely used) and (ii) ring-based. The former consists of a semi-circular reduction of the annulus in the posterior portion. In theory, the technique offers advantages over ring annuloplasty, as it conserves the dynamics of the valve and preserves its saddle shape; however, this remains to be clinically proven. Short-term and midterm results have shown effectiveness. On the long term, a trend toward recurrence of annular dilation was observed. An example of a current ring-based open-heart intervention involves suturing the annulus to a prosthetic ring that reduces the valve area to normal or undersized systolic dimensions. Its advantage lies in its reproducibility, its ability to conserving dimensions over time, its low sensitivity to different dilated annulus geometries and an even stress distribution over the suture attachments, which are carefully inserted in the fibrous annulus. In functional MR of type-1/type-3b, the ring-based technique has established itself as the preferred technique with very good results. On the other hand, suture-based techniques that remodel only the posterior annulus have shown poor reproducibility and poor long-term results with a recurrence of MR.
The interest of the industry in developing percutaneous mitral valve repair is high, as reflected by the large number of companies working on the problem. Two distinct categories of repair are being developed: (i) edge-to-edge repair and (ii) annuloplasty. Mainly targeting type-2 patients, the edge-to-edge repair replicates the Alfieri stitch; this consists in installing, via a catheter, a clip or suture, at the mid-portion of the valve, intended to grasp and fasten together the leaflets, at their edge midpoints, to create a double orifice. This manoeuvre increases leaflet coaptation and eliminates focal excessive leaflet motion when present. In conventional surgery, when the edge-to-edge technique is combined with annuloplasty, results are reportedly very good. However, when annuloplasty is not used, it is less effective. A percutaneous edge-to-edge repair by itself does not result in major improvements of the condition of the patient, its application being limited. On the other hand, percutaneous annuloplasty has attracted much more interest. It is useful in all cases of mitral valve repair, regardless of the etiology, and is the main correction for type-1 and type-3b patients.
Currently, many different percutaneous annuloplasties are being developed; in direct techniques, the repair affects explicitly the annulus, while in indirect techniques, a change in proximal structure leads to annulus reshaping. Five current approaches are worth mentioning: a) indirect annuloplasty via the coronary sinus (CS); b) atrial annular cinching (indirect); c) ventricular remodeling (indirect); d) transventricular suture-based method (direct); and e) energy-based annulus-shrinkage devices that use radiofrequency (RF) at sub-ablative temperatures to produce contraction of the annulus collagen (direct). Based on the literature, direct-annuloplasty techniques are more robust than indirect techniques, since they are much less sensitive to the variation in anatomy between patients and have a higher reproducibility. For example, CS-based methods require the CS to be circumferentially adjacent, on a same plane, to the annulus, which is not always the case and a risk of squeezing the circumflex artery exists. In addition, there is no background knowledge for using other indirect techniques, and longterm effects are still unknown. It is important to note a specificity of technique (c), which addresses two issues with one device, by cinching the ventricle using a transventricular cord, it indirectly squeezes the mitral annulus while countering the ventricle dilation. Such technique is regarded by many professionals as too aggressive. A trade-of between safety and performance is observed in all the techniques; none offers comparable results to rigid-ring annuloplasty, which is strong in nearly all criteria. Technique d) above achieves a partial reduction of MR without its abolition. This is intrinsically linked to the device function of reshaping only the posterior side of the annulus. The major limitation of these technique lies in their reliance on conventional manually controlled catheter, with which interventionalists can only access, from the ventricle (retrograde approach), the posterior portion of the mitral where anchors are inserted.
There therefore seems to be a need for an improved percutaneous annuloplasty. However, such annuloplasty requires precise positioning of an instrument in the heart of a patient with respect to moving tissue, which is relatively difficult to achieve. Also, while an emphasis on cardiac interventions has been made in the previous paragraphs, there are many other situations in which positioning of an instrument with respect to a moving tissue has to be performed precisely
Against this background, there exists a need in the industry to provide novel instrument positionable with respect to a moving tissue. An object of the present invention is therefore to provide improved methods and devices for positioning instruments with respect to a moving tissue.